The present invention relates generally to probing contacts and more particularly to a low capacitance probe contact.
Probing contacts used with logic analyzer and the like have parallel finger contacts that fit onto pins mounted on a circuit board having a fixed spacing between pins. The fingers have a flat portion on one end that are soldered to a substrate containing electrical circuitry that isolates the circuit under test from electrical loading by the measuring instrument. The flat portions are randomly oriented in relation to the fingers. Electrically conductive barrels are positioned over the finger contacts. The substrate and the barrels are overmolded with plastic with the barrels shielding the contact fingers from invasion by the overmolding plastic. The barrels force the circuit board mounted pins to enter the fingers in only one orientation and increase the overall diameter of the contact resulting in a higher capacitance between the contacts.
What is needed is a low capacitance probe contact for logic analyzers that overcomes the higher capacitance of parallel probe contacts housed in barrels. The probe contact should also allow for connection to pins having different center to center pin spacing and accept pins of different diameters.
Accordingly, the present invention is to a low capacitance probe contact having at least first and second electrically conductive contacts with fingers having opposing interior flat surfaces forming a slit there between. The fingers extend in a first direction with a mounting member extending in the opposite direction having a flat surface that is parallel to the flat surfaces of the fingers. The first and second electrically conductive contacts are secured to respective first and second electrically conductive contact pads formed on a substrate with the flat surfaces of the mounting members being positioned on the contact pads. The substrate and the first and second electrically conductive contacts are captured within a housing having first and second members. One of the members has a base and extending sidewalls forming a recess that receives the substrate and the first and second electrically conductive contacts. The other member has a periphery that is coextensive with the sidewalls and is secured to the sidewalls to capture the substrate and the first and second electrically conductive contacts within the housing.
In one embodiment, the first and second electrically conductive contacts are parallel to each other while in the preferred embodiment the contacts are inwardly angled such that the distal ends of the fingers are closer together than the mounting members secured to the substrate. The distal ends of the fingers are angled outward to facilitate the acceptance of pin contacts. The substrate has electrical circuitry mounted thereon having inputs electrically coupled to the first and second electrically conductive contact pads. The electrical circuitry minimizes electrical loading of signals under test coupled to the first and second electrically conductive contacts. Electrical leads are coupled to outputs of the electrical circuitry and extend from the housing. The space between the fingers of the first and second electrically conductive contacts has a substantially air dielectric insulator having a dielectric constant approximating the dielectric constant of air.